1. Field of the Invention
The present invention is directed to a screw driving machine employing a screw conveyance belt which is made of a long, relatively narrow, sheet or of a long wide sheet folded on itself so as to form a belt. The shanks of screws are inserted through the belt at prescribed intervals so as to be supported by the belt. In particular, the present invention is a screw driving machine with a support and guides system for the screw conveyance belt.
2. Description of the Related Art
The screw conveyance belt of a conventional screw driving machine is not very long. Therefore, the belt is fitted in a screw conveyance belt feed mechanism provided in the nose member of the machine and is allowed to hang freely at portions of the belt outside of the feed mechanism. The belt flexes relatively easily due to the weight of the screws held and typically has notches on one edge for engagement by the feed claw of the belt feed mechanism. Therefore, if the belt is twisted halfway during the screw driving operation of the machine, the notch or the shank of the screw is likely to become caught upon entering the feed mechanism, thus hindering the feed of the screws. This is a problem particularly when the inclination of the end of the belt, which is held by the belt feed mechanism, and that of other portions of the belt, which hang down due to gravity, are different from each other as in the case where the machine is inclined at an angle. In such a case, the belt is twisted so that the notch thereof or the shank of the screw is more likely to get caught upon entering the feed mechanism. In addition, since the belt freely sways at the free portions every time the machine is moved, the belt is likely to interfere with the screw driving operation at the free end of the belt. For these reasons, the belt usually needs to be held at the free end by the person operating the machine.
To solve these problems, a screw driving machine having a guide member, provided for the screw conveyance belt, located at the side of the machine was developed as disclosed in the Japan Utility Model Application No. 26921/85. Although the movement of the belt into the screw conveyance belt feed mechanism is improved by the guide member, the belt is likely to become caught on the guide member at the belt inlet portion thereof. Still, the belt needs to be held at the free end thereof by an operator until some of the screws supported by the belt have been driven so that the flexure of the belt is minimized. Therefore, the efficiency of the screw driving operation of such machine is still not optimized.